Is “Grey’s Anatomy” star Katherine Heigl trying to upstage co-star Ellen Pompeo on the motherhood front? Heigl made public her adoption of a 10-month-old Korean daughter, Naleigh, on Sept. 15 — which just happened to be the same day that Pompeo gave birth to a daughter of her own. “It was very curious timing for her to drop that,” a source who knows both women tells Page Six, adding, “It was an adopted kid — she could have chosen any other day to make it public. Why compete?” Pompeo didn’t confirm to the press the birth of her own little girl until Wednesday, which was the same day Heigl and her daughter appeared on the cover of People magazine. “It looks like they were trying to one-up one another,” laughs our spy. Reps for both Heigl and Pompeo declined to comment.